1. Field of the Invention
The present invention generally relates to graphics processing. More specifically, the present invention relates to techniques for rendering an image using sampling methods suited for graphics hardware acceleration.
2. Description of the Related Art
In computer graphics, rendering is the process of determining color values of the pixels of a two dimensional graphics image based on a three-dimensional graphics scene typically generated by a graphics application. When graphics images are rendered, various artifacts, such as jagged edges, may ultimately appear in the image. A number of anti-aliasing techniques exist that “blend” the colors of pixels adjacent to one another in an image to mask artifacts in the image. For example, such blending can make jagged edges appear smoother to the human eye. Typical anti-aliasing techniques use multiple color values or samples to determine the final color value of each pixel in the graphics image so that there is a more gradual transition between the different objects and colors in the graphics image.
Currently, random and pseudo random sampling methods have been used to reduce aliasing effects when generating images using a software-based rendering engine. This approach has the advantage of using a random sampling pattern for anti-aliasing so that the sampling frequencies are less likely to correlate with the spatial frequencies in the graphics image, but requires that the image be rendered by software routines that execute on a general purpose central processing unit (CPU). While effective, the software approach is significantly slower than using hardware based rendering techniques.
In contrast to software renderers, dedicated graphics processing units (GPUs) typically use a fixed sampling pattern to perform anti-aliasing operations. GPUs are specifically designed to process image data much more quickly than a CPU. However, the sampling patterns used by GPUs may introduce moiré, ringing, or animation artifacts for some images. Moiré effects are most often generated when the sampling frequency of the anti-aliasing grid pattern correlates with one or more spatial frequencies present in the graphics image. For example, images that include regular patterns such as roof lines or brick walls, checkerboards, or any other repeating pattern in an image may lead to moiré effects when using anti-aliasing techniques that rely on grid-based sampling.
Accordingly, what is needed in the art is a sampling technique suited for graphics hardware acceleration that is not as prone to artifacts, such as moiré effects, as current hardware-based sampling techniques.